1. Field of the Invention
Embodiments of the invention relate to a method of correcting a preferred color using previously determined parameters without performing an analysis process of an input image and a display device capable of increasing display quality using the correcting method.
2. Discussion of the Related Art
Various flat panel displays whose weight and size are smaller than cathode ray tubes have been developed. Examples of the flat panel displays include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), and an electroluminescence device (EL). The electroluminescence device includes an organic light emitting diode (OLED).
In an active matrix thin film transistor (AM TFT) LCD, a TFT is formed in each pixel. The AM TFT LCD has been implemented in televisions as well as display devices in portable devices, such as office equipment and computers. Accordingly, cathode ray tubes are being rapidly replaced by the AM TFT LCD.
Display quality of display devices has been evaluated by subjective evaluation of a viewer about a preferred color reproduction. A preferred color correcting technology has been used to increase the display quality of the display devices.
There are a region correcting method and a point correcting method as the preferred color correcting method. For example, “Preferred Skin Color Reproduction Based on Adaptive Affine Transform” (IEEE Transactions on Consumer Electronics, Vol. 51, No. 1, pp 191-197, 2005) corresponding to the region correcting method, “Skin color reproduction algorithm for portrait images shown on the mobile display” (SPIE vol. 6058, pp 1-8) corresponding to the point correcting method, and the like, are well known. In the region correcting method, an input color range and a preferred color range are determined as an oval shape in u′v′ chromaticity coordinates, and then the input color range is mapped to the preferred color range. In the point correcting method, a target is selected as one point of a color space, and an input color is corrected to a color similar to the target. However, in the region correcting method, a contour noise is generated, and a luminance is reduced because there is no brightness correction. In the point correcting method, a preferred color correction performance is reduced because content of an input image is not considered. So as to solve the problems of the contour noise and the luminance reduction generated in the existing preferred color correcting method, an average value of a preferred color in the chromaticity coordinates and a preferred color correcting method according to a reference value of the preferred color were proposed through Korea Patent Application No. 10-2007-0061992 (Jun. 25, 2007) corresponding to the present applicant, and which are hereby incorporated by reference in their entirety.
The preferred color correcting method has recently developed greatly, but problems to be solved still remain. Thus, it is difficult to achieve the preferred color correcting method in the liquid crystal display. Most of preferred color correcting methods are implemented through the following two processes (1) and (2).
The first process (1) is a conversion process into a uniform color space for preferred color mapping by correcting each of brightness “L”, chroma “C”, and hue “H”. A complex operational process is necessary in the conversion process, and thus complexity of hardware and processing time are excessively delayed.
The second process (2) is a process for detecting a preferred color region in an input image frame or analyzing a color distribution so as to design a preferred color conversion module. The preferred color conversion module may be divided into a module for analyzing a color distribution of an input image, a module for extracting primary colors based on an analysis result, a module for determining a conversion region to be processed in a color space based on a distribution of the primary colors extracted from the input image, a module for converting a color belonging to the conversion region among colors constituting the input image, and the like. Because it is difficult to implement the preferred color conversion module as a lookup table, it is difficult to real-time perform the existing preferred color correcting method. Further, it is difficult to perform multi-primary color reproduction.